The present invention relates to an improvement in bead members for use in pneumatic tires for reducing the weight and fuel cost of vehicles.
With arguments focused on limitations on petroleum supplies in recent years, efficient use of derivatives of petroleum is now at issue. For savings of energy, the problem of fuel cost has attracted much attention in the automotive industry. For the reduction of fuel cost, aerodynamic improvements in the vehicle construction, as well as improved engine efficiencies, are most desirable, and it is also desired to reduce the weight of the vehicle and that of the tire as a component thereof.
In place of steel wires conventionally used as bead members in tires, it has been proposed to use so-called aramid cords which are composed only of a light-weight organic fiber having a high modulus. However, aramid cords have poor stability and are extremely difficult to handle for the production of tires. To solve this problem, U.S. Pat. No. 3,942,574 discloses a tire bead comprising aramid cords and a metal cord disposed alongside the aramid cords for stabilizing the aramid cords and rigidifying the bead. Although having increased rigidity and made easier to handle during the molding of tires, the bead still remains to be improved for the reduction of its weight since it has incorporated therein the metal cord. Additionally the conjoint use of aramid and metal cords involves the drawback of rendering the bead structure complex.